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Vivaldi vs SeaMonkey: catalog facts
Vivaldi	SeaMonkey
Free Free, funded by default search engine and bookmark placement deals.	Free The software is free under its open-source licence. Hosting, hardware and external…
Windows, macOS, Linux, Android, iOS	Windows, macOS, Linux
Tab stacking, tiling and vertical tabs without a single extension Built-in mail, calendar and feed reader in a side panel	It is the continuation of the old Mozilla Application Suite, so browsing, mail, news and page editing live…
Not open source; only the modified Chromium parts are published The sheer number of settings takes real time to work through	It tracks an older Firefox codebase, so web compatibility and security hardening trail the current browsers.
Downloadable app	Downloadable app
Closed source	Open source
License not stated	License: MPL-2.0
No account needed	Not stated if an account is needed
Needs internet	Not stated if it works offline
Official website Full listing and sources Checked September 21, 2026	Official website Full listing and sources Checked September 22, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.